This invention relates to processes for producing carbamates using certain metal-containing catalyst compositions. More particularly, the invention relates to processes for producing carbamates by reacting amines and/or ureas, carbon monoxide, organic hydroxyl components and an oxygen-containing oxidizing agent in the presence of certain metal-containing catalyst compositions.
Carbamates, or urethanes, are useful, for example, in producing isocyanates and as pesticides. The desired isocyanate can often be obtained by thermally decomposing the carbamate. A number of different methods have been suggested for producing carbamates.
Zajacek et al U.S. Pat. Nos. 3,895,054 and 3,956,360 disclose a process for preparing urethanes by reacting an organic hydroxyl compound with carbon monoxide and a nitrogenous organic compound, such as an organic nitro compound, in the presence of a catalyst containing sulfur and/or selenium and/or tellurium and at least one of base and water. A number of patents disclose the use of selenium and/or sulfur and/or tellurium as a catalyst for the conversion of amines to carbamates and ureas, which can be used as precursors to carbamates. See, for example, Hirai et al U.S. Pat. No. 4,170,708; Scholl et al U.S. Pat. Nos. 4,236,016; 4,267,353; and 4,490,551; and Moy U.S. Pat. Nos. 4,242,520 and 4,258,201.
Various processes based on the use of platinum group metal catalysts to promote the formation of urethanes/carbamates from organic hydroxyl compounds, carbon monoxide, organic nitrogen compounds, such as organic nitrocompounds or amines, and possibly an oxygen-containing oxidizing agent have been suggested. See, for example, Zajacek et al U.S. Pat. No. 3,993,685; Becker et al U.S. Pat. Nos. 4,297,501 and 4,339,592; Stammann et al U.S. Pat. No. 4,582,923; Hirai et al U.S. Pat. No. 4,186,269, Fukuoka et al U.S. Pat. No. 4,621,149; and Grate et al U.S. Pat. No. 4,600,793. Moy U.S. Pat. No. 4,266,070 disclose a process for producing urethanes by reacting an organic primary or secondary amine, in the absence of reactive oxygen, with carbon monoxide and an organic hydroxyl component using a catalyst of carbonyls of cobalt, molybdenum, titanium, rhodium, iron and nickel. In many instances, a co-catalyst component is required. Also, the catalysts often tend to become deactivated, or even decompose, at reaction conditions. Thus, if the catalytically active metal is to be reused, it may have to be recovered from the product and reactivated, or even reconstituted, before such reuse. Catalyst compositions which do not require co-catalysts and/or which have enhanced stability at reaction conditions would clearly be advantageous.
Pretzer et al U.S. Pat. No. 4,151,208 discloses a process for producing acetaldehyde from methanol, hydrogen and carbon monoxide using a cobalt (II) meso-tetraaromaticporphine catalyst and an iodine promoter. Pesa et al U.S. Pat. No. 4,271,038 discloses a process for producing aldehydes by the reaction of carbon monoxide, hydrogen and olifinically unsaturated compounds in the presence of a catalyst of cobalt carbonyl and porphyrin promoter ligand. Neither of these two patents discloses or even suggests carbamate production.
Relatively recent work reported by Italian researchers has disclosed that anilines can be oxidized to azobenzenes in methanol or methylene chloride solution using dioxygen as the oxidant and bis (salicylaldehyde) ethylenediimine cobalt (II) as catalyst. In the presence of carbon monoxide, isocyanates, urethanes and ureas are also obtained. See: Benedini, et al, "The Bis (salicylaldehyde) ethylene diimine Cobalt (II)-catalyzed Oxidative Carbonylation of Primary and Secondary Amines", Journal of Molecular Catalysis, 34 (1986) 155-161; and Maddinelli, et al, "The Bis (salicylaldehyde) ethylenediimine Cobalt II - catalyzed Oxidative Carbonylation of 1-Adamantylamine in Alcohol: A Study for Optimizing Carbamate Formation", Journal of Molecular Catalysis, 39 (1987) 71-77. No other catalysts, and no reaction promoters, are disclosed or suggested by this work.
There continues to be a need for a process for producing carbamates.